Neighbor cell measurement and reselection for narrowband operation

ABSTRACT

Aspects of the present disclosure provide techniques that may be utilized by a UE for performing neighbor cell measurement and reselection in narrowband deployment scenarios, such as NB-IoT deployment scenarios. For example, a method for wireless communications by a user equipment (UE), can include determining, while communicating in a serving cell, information regarding one or more transmission deployment mode parameters of at least one neighbor cell, and performing a neighbor cell search with measurement of narrowband reference signals (NRS) based on the one or more transmission deployment mode parameters.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application for Patent claims benefit of U.S. ProvisionalPatent Application Ser. No. 62/501,311, filed May 4, 2017, assigned tothe assignee hereof and hereby expressly incorporated by referenceherein.

BACKGROUND Field of the Disclosure

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to neighbor cell measurement andreselection procedures in narrowband applications.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE)/LTE-Advanced systems andorthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-input single-output, multiple-inputsingle-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of base stationsthat can support communication for a number of wireless devices.Wireless devices may include user equipments (UEs). Machine typecommunications (MTC) may refer to communication involving at least oneremote device on at least one end of the communication and may includeforms of data communication which involve one or more entities that donot necessarily need human interaction. MTC UEs may include UEs that arecapable of MTC communications with MTC servers and/or other MTC devicesthrough Public Land Mobile Networks (PLMN), for example. Wirelessdevices may include narrowband Internet-of-Things (NB-IoT) devices. IoTmay refer to a network of physical objects, devices, or “things”. IoTdevices may be embedded with, for example, electronics, software, orsensors and may have network connectivity, which enable these devices tocollect and exchange data.

Some next generation, NR, or 5G networks may include a number of basestations, each simultaneously supporting communication for multiplecommunication devices, such as UEs. In LTE or LTE-A network, a set ofone or more base stations may define an e NodeB (eNB). In other examples(e.g., in a next generation or 5G network), a wireless multiple accesscommunication system may include a number of distributed units (e.g.,edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads(SRHs), transmission reception points (TRPs), etc.) in communicationwith a number of central units (e.g., central nodes (CNs), access nodecontrollers (ANCs), etc.), where a set of one or more distributed units,in communication with a central unit, may define an access node (e.g., anew radio base station (NR BS), a new radio node-B (NR NB), a networknode, gNB, etc.). A base station or DU may communicate with a set of UEson downlink channels (e.g., for transmissions from a base station or toa UE) and uplink channels (e.g., for transmissions from a UE to a basestation or distributed unit).

Some next generation, NR, or 5G networks may support an uplink-basedmedium access control (MAC) layer. In these networks, a UE may transmita pilot signal (e.g., a reference signal) for network access devices(e.g., distributed units) to receive and measure. Based on measurementsof the pilot signal by one or more network access devices, the networkmay identify a serving cell (or serving distributed unit) for the UE. Asthe UE moves within the network, the network may make at least somemobility decisions for the UE (e.g., decisions to initiate a handover ofthe UE from one serving cell to another serving cell) transparently tothe UE (e.g., without notifying the UE of the mobility decision, orwithout involving the UE in the mobility decision).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess. NR is a set of enhancements to the LTE mobile standardpromulgated by 3GPP. It is designed to better support mobile broadbandInternet access by improving spectral efficiency, lowering costs,improving services, making use of new spectrum, and better integratingwith other open standards using OFDMA with a cyclic prefix (CP) on thedownlink (DL) and on the uplink (UL) as well as support beamforming,MIMO antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in LTE, MTC, IoT,and NR technology. Preferably, these improvements should be applicableto other multi-access technologies and the telecommunication standardsthat employ these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “DETAILED DESCRIPTION” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure generally relate to neighborcell measurement and reselection procedures in narrowband applications,such as narrowband Internet-of-Things (NB-IoT) applications.

Certain aspects of the present disclosure provide a method, performed bya user equipment (UE). The method generally includes determining, whilecommunicating in a serving cell, information regarding one or moretransmission deployment mode parameters of at least one neighbor celland performing a neighbor cell search with measurement of narrowbandreference signals (NRS) based on the one or more transmission deploymentmode parameters.

Numerous other aspects are provided including methods, apparatus,systems, computer program products, computer-readable medium, andprocessing systems. To the accomplishment of the foregoing and relatedends, the one or more aspects comprise the features hereinafter fullydescribed and particularly pointed out in the claims. The followingdescription and the annexed drawings set forth in detail certainillustrative features of the one or more aspects. These features areindicative, however, of but a few of the various ways in which theprinciples of various aspects may be employed, and this description isintended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an example of awireless communication network, in accordance with certain aspects ofthe present disclosure.

FIG. 2 shows a block diagram conceptually illustrating an example of abase station (BS) in communication with a user equipment (UE) in awireless communications network, in accordance with certain aspects ofthe present disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of aframe structure in a wireless communications network, in accordance withcertain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating two exemplarysubframe formats with the normal cyclic prefix, in accordance withcertain aspects of the present disclosure.

FIG. 5 illustrates an exemplary subframe configuration for enhancedmachine type communications (eMTC), in accordance with certain aspectsof the present disclosure.

FIG. 6 illustrates an example deployment of narrowbandInternet-of-Things (NB-IoT), in accordance with certain aspects of thepresent disclosure.

FIG. 7 illustrates an example logical architecture of a distributedradio access network (RAN), in accordance with certain aspects of thepresent disclosure.

FIG. 8 illustrates an example physical architecture of a distributedRAN, in accordance with certain aspects of the present disclosure.

FIG. 9 is a diagram illustrating an example of a downlink (DL)-centricsubframe, in accordance with certain aspects of the present disclosure.

FIG. 10 is a diagram illustrating an example of an uplink (UL)-centricsubframe, in accordance with certain aspects of the present disclosure.

FIG. 11 illustrates example operations that may be performed by a UE forneighbor cell measurement and reselection, in accordance with certainaspects of the present disclosure.

FIG. 11A illustrates example components capable of performing theoperations shown in FIG. 11.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements described in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques that may beutilized by a UE for performing neighbor cell measurement andreselection, for example, in NB-IoT deployment scenarios.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). New Radio (NR) (e.g., 5G radio access)is an example of an emerging telecommunication standard. NR is a set ofenhancements to the LTE mobile standard promulgated by 3GPP. Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, certain aspects of the techniquesare described below for LTE/LTE-Advanced, and LTE/LTE-Advancedterminology is used in much of the description below. LTE and LTE-A arereferred to generally as LTE. For clarity, while aspects may bedescribed herein using terminology commonly associated with 3G and/or 4Gwireless technologies, aspects of the present disclosure can be appliedin other communication systems, such as 5G and later, including NRtechnologies.

EXAMPLE WIRELESS COMMUNICATIONS NETWORK

FIG. 1 illustrates an example wireless communication network 100, inwhich aspects of the present disclosure may be practiced. For example,techniques presented herein may be used for neighbor cell measurementand reselection procedures in bandwidth limited (BL)/coverageenhancement (CE) applications, for example, machine typecommunication(s) (MTC), enhanced MTC (eMTC), and/or narrowbandInternet-of-Things (NB-IoT).

The network 100 may be an LTE network or some other wireless network.Wireless communication network 100 may include a number of BSs 110 andother network entities. A BS is an entity that communicates with userequipments (UEs) and may also be referred to as a e Node B (eNB), a NodeB, an access point, a 5G NB, gNB, transmission reception point (TRP), anew radio (NR) BS, etc. Each BS may provide communication coverage for aparticular geographic area. In 3GPP, the term “cell” can refer to acoverage area of an BS and/or an BS subsystem serving this coveragearea, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). A BS for a macro cell may bereferred to as a macro BS. A BS for a pico cell may be referred to as apico BS. A BS for a femto cell may be referred to as a femto BS or ahome BS. In the example shown in FIG. 1, a BS 110 a may be a macro BSfor a macro cell 102 a, a BS 110 b may be a pico BS for a pico cell 102b, and a BS 110 c may be a femto BS for a femto cell 102 c. A BS maysupport one or multiple (e.g., three) cells. The terms “eNB”, “basestation” and “cell” may be used interchangeably herein.

Wireless communication network 100 may also include relay stations. Arelay station is an entity that can receive a transmission of data froman upstream station (e.g., a BS or a UE) and send a transmission of thedata to a downstream station (e.g., a UE or a BS). A relay station mayalso be a UE that can relay transmissions for other UEs. In the exampleshown in FIG. 1, a relay station 110 d may communicate with macro BS 110a and a UE 120 d in order to facilitate communication between BS 110 aand UE 120 d. A relay station may also be referred to as a relay BS, arelay base station, a relay, etc.

Wireless communication network 100 may be a heterogeneous network thatincludes BSs of different types, e.g., macro BSs, pico BSs, femto BSs,relay BSs, etc. These different types of BSs may have different transmitpower levels, different coverage areas, and different impact oninterference in wireless communication network 100. For example, macroBSs may have a high transmit power level (e.g., 5 to 40 Watts) whereaspico BSs, femto BSs, and relay BSs may have lower transmit power levels(e.g., 0.1 to 2 Watts).

A network controller 130 may couple to a set of BSs and may providecoordination and control for these BSs. Network controller 130 maycommunicate with the BSs via a backhaul. The BSs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wirelesscommunication network 100, and each UE may be stationary or mobile. A UEmay also be referred to as an access terminal, a terminal, a mobilestation, a subscriber unit, a station, etc. A UE may be a cellular phone(e.g., a smart phone), a personal digital assistant (PDA), a wirelessmodem, a wireless communication device, a handheld device, a laptopcomputer, a cordless phone, a wireless local loop (WLL) station, atablet, a camera, a netbook, a smartbook, an ultrabook, a drone, arobot, a sensor, a monitor, a meter, a camera/security camera, agaming/entertainment device, a virtual reality/augmented reality device,a wearable device (e.g., smart watch, smart glasses, virtual realitygoggles/helmet/glove/body suit, smart ring, smart bracelet, smart wristband, smart jewelry, smart clothing, etc.), a vehicular/telematicsdevice, a position location/navigation device (e.g., satellite-based,terrestrial-based, etc.), a medical/healthcare device, etc. Some UEs maybe considered machine-type communication (MTC) UEs, which may includeremote devices, that may communicate with a base station, another remotedevice, or some other entity. Machine type communications (MTC) mayrefer to communication involving at least one remote device on at leastone end of the communication and may include forms of data communicationwhich involve one or more entities that do not necessarily need humaninteraction. MTC UEs may include UEs that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMN), for example. Examples of MTC devicesinclude sensors, meters, location tags, monitors, drones, robots/roboticdevices, etc. MTC UEs, as well as other types of UEs, may be implementedas NB-IoT (narrowband internet of things) devices. In FIG. 1, a solidline with double arrows indicates desired transmissions between a UE anda serving BS, which is an eNB designated to serve the UE on the downlinkand/or uplink. A dashed line with double arrows indicates potentiallyinterfering transmissions between a UE and an BS.

FIG. 2 shows a block diagram of a design of BS 110 and UE 120, which maybe one of the base stations/eNBs and one of the UEs in FIG. 1. BS 110may be equipped with T antennas 234 a through 234 t, and UE 120 may beequipped with R antennas 252 a through 252 r, where in general T≥1 andR≥1.

At base station 110, a transmit processor 220 may receive data from adata source 212 for one or more UEs, select one or more modulation andcoding schemes (MCS) for each UE based on CQIs received from the UE,process (e.g., encode and modulate) the data for each UE based on theMCS(s) selected for the UE, and provide data symbols for all UEs.Transmit processor 220 may also process system information (e.g., forSRPI, etc.) and control information (e.g., CQI requests, grants, upperlayer signaling, etc.) and provide overhead symbols and control symbols.Processor 220 may also generate reference symbols for reference signals(e.g., the CRS) and synchronization signals (e.g., the PSS and SSS). Atransmit (TX) multiple-input multiple-output (MIMO) processor 230 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, the overhead symbols, and/or the reference symbols, ifapplicable, and may provide T output symbol streams to T modulators(MODs) 232 a through 232 t. Each modulator 232 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 232 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. T downlink signals from modulators 232 a through 232 tmay be transmitted via T antennas 234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom base station 110 and/or other base stations and may providereceived signals to demodulators (DEMODs) 254 a through 254 r,respectively. Each demodulator 254 may condition (e.g., filter, amplify,downconvert, and digitize) its received signal to obtain input samples.Each demodulator 254 may further process the input samples (e.g., forOFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtainreceived symbols from all R demodulators 254 a through 254 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 258 may process (e.g., demodulateand decode) the detected symbols, provide decoded data for UE 120 to adata sink 260, and provide decoded control information and systeminformation to a controller/processor 280. A channel processor maydetermine RSRP, RSSI, RSRQ, CQI, etc.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, etc.) fromcontroller/processor 280. Processor 264 may also generate referencesymbols for one or more reference signals. The symbols from transmitprocessor 264 may be precoded by a TX MIMO processor 266 if applicable,further processed by modulators 254 a through 254 r (e.g., for SC-FDM,OFDM, etc.), and transmitted to base station 110. At base station 110,the uplink signals from UE 120 and other UEs may be received by antennas234, processed by demodulators 232, detected by a MIMO detector 236 ifapplicable, and further processed by a receive processor 238 to obtaindecoded data and control information sent by UE 120. Processor 238 mayprovide the decoded data to a data sink 239 and the decoded controlinformation to controller/processor 240. BS 110 may includecommunication unit 244 and communicate to network controller 130 viacommunication unit 244. Network controller 130 may include communicationunit 294, controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at basestation 110 and UE 120, respectively, to perform techniques presentedherein for HARQ timing for HARQ ID determination for MTC to use forcommunications between a UE (e.g., an eMTC UE or NB-IoT device) and abase station (e.g., an eNodeB, TRP, AP, NB, 5G NB, NR BS, gNB, etc.).For example, processor 240 and/or other processors and modules at basestation 110, and processor 280 and/or other processors and modules at UE120, may perform or direct operations of base station 110 and UE 120,respectively. For example, controller/processor 280 and/or othercontrollers/processors and modules at UE 120, and/orcontroller/processor 240 and/or other controllers/processors and modulesat BS 110 may perform or direct operations 1100 shown in FIG. 11.Memories 242 and 282 may store data and program codes for base station110 and UE 120, respectively. A scheduler 246 may schedule UEs for datatransmission on the downlink and/or uplink.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as ascheduling entity. That is, in some examples, a UE may function as ascheduling entity, scheduling resources for one or more subordinateentities (e.g., one or more other UEs). In this example, the UE isfunctioning as a scheduling entity, and other UEs utilize resourcesscheduled by the UE for wireless communication. A UE may function as ascheduling entity in a peer-to-peer (P2P) network, and/or in a meshnetwork. In a mesh network example, UEs may optionally communicatedirectly with one another in addition to communicating with thescheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

FIG. 3 shows an exemplary frame structure 300 for FDD in a wirelesscommunication system (e.g., LTE). The transmission timeline for each ofthe downlink and uplink may be partitioned into units of radio frames.Each radio frame may have a predetermined duration (e.g., 10milliseconds (ms)) and may be partitioned into 10 subframes with indicesof 0 through 9. Each subframe may include two slots. Each radio framemay thus include 20 slots with indices of 0 through 19. Each slot mayinclude L symbol periods, e.g., seven symbol periods for a normal cyclicprefix (as shown in FIG. 3) or six symbol periods for an extended cyclicprefix. The 2L symbol periods in each subframe may be assigned indicesof 0 through 2L-1.

In certain wireless communication systems (e.g., LTE), a BS may transmita primary synchronization signal (PSS) and a secondary synchronizationsignal (SSS) on the downlink in the center of the system bandwidth foreach cell supported by the BS. The PSS and SSS may be transmitted insymbol periods 6 and 5, respectively, in subframes 0 and 5 of each radioframe with the normal cyclic prefix, as shown in FIG. 3. The PSS and SSSmay be used by UEs for cell search and acquisition. The BS may transmita cell-specific reference signal (CRS) across the system bandwidth foreach cell supported by the eNB. The CRS may be transmitted in certainsymbol periods of each subframe and may be used by the UEs to performchannel estimation, channel quality measurement, and/or other functions.The BS may also transmit a physical broadcast channel (PBCH) in symbolperiods 0 to 3 in slot 1 of certain radio frames. The PBCH may carrysome system information. The BS may transmit other system informationsuch as system information blocks (SIBs) on a physical downlink sharedchannel (PDSCH) in certain subframes. The BS may transmit controlinformation/data on a physical downlink control channel (PDCCH) in thefirst B symbol periods of a subframe, where B may be configurable foreach subframe. The BS may transmit traffic data and/or other data on thePDSCH in the remaining symbol periods of each subframe.

In certain systems (e.g., such as NR or 5G systems), a BS may transmitthese or other signals in these locations or in different locations ofthe subframe.

FIG. 4 shows two exemplary subframe formats 410 and 420 with the normalcyclic prefix. The available time frequency resources may be partitionedinto resource blocks. Each resource block may cover 12 subcarriers inone slot and may include a number of resource elements. Each resourceelement may cover one subcarrier in one symbol period and may be used tosend one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may betransmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11. Areference signal is a signal that is known a priori by a transmitter anda receiver and may also be referred to as pilot. A CRS is a referencesignal that is specific for a cell, e.g., generated based on a cellidentity (ID). In FIG. 4, for a given resource element with label Ra, amodulation symbol may be transmitted on that resource element fromantenna a, and no modulation symbols may be transmitted on that resourceelement from other antennas. Subframe format 420 may be used with fourantennas. A CRS may be transmitted from antennas 0 and 1 in symbolperiods 0, 4, 7 and 11 and from antennas 2 and 3 in symbol periods 1 and8. For both subframe formats 410 and 420, a CRS may be transmitted onevenly spaced subcarriers, which may be determined based on cell ID.CRSs may be transmitted on the same or different subcarriers, dependingon their cell IDs. For both subframe formats 410 and 420, resourceelements not used for the CRS may be used to transmit data (e.g.,traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211,entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); PhysicalChannels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplinkfor FDD in LTE. For example, Q interlaces with indices of 0 through Q-1may be defined, where Q may be equal to 4, 6, 8, 10, or some othervalue. Each interlace may include subframes that are spaced apart by Qframes. In particular, interlace q may include subframes q, q+Q, q+2Q,etc., where qϵ{0, . . . , Q-1}.

The wireless network may support hybrid automatic retransmission request(HARQ) for data transmission on the downlink and uplink. For HARQ, atransmitter (e.g., an eNB) may send one or more transmissions of apacket until the packet is decoded correctly by a receiver (e.g., a UE)or some other termination condition is encountered. For synchronousHARQ, all transmissions of the packet may be sent in subframes of asingle interlace. For asynchronous HARQ, each transmission of the packetmay be sent in any subframe.

A UE may be located within the coverage of multiple BSs. One of theseBSs may be selected to serve the UE. The serving BS may be selectedbased on various criteria such as received signal strength, receivedsignal quality, pathloss, etc. Received signal quality may be quantifiedby a signal-to-noise-and-interference ratio (SINR), or a referencesignal received quality (RSRQ), or some other metric. The UE may operatein a dominant interference scenario in which the UE may observe highinterference from one or more interfering BSs.

EXAMPLE ENHANCED MACHINE TYPE COMMUNICATIONS (EMTC)

The focus of traditional LTE design (e.g., for legacy “non MTC” devices)is on the improvement of spectral efficiency, ubiquitous coverage, andenhanced quality of service (QoS) support. Current LTE system downlink(DL) and uplink (UL) link budgets are designed for coverage of high enddevices, such as state-of-the-art smartphones and tablets, which maysupport a relatively large DL and UL link budget.

However, low cost, low rate devices need to be supported as well. Forexample, certain standards (e.g., LTE Release 12) have introduced a newtype of UE (referred to as a category 0 UE) generally targeting low costdesigns or machine type communications. For machine type communications(MTC), various requirements may be relaxed as only a limited amount ofinformation may need to be exchanged. For example, maximum bandwidth maybe reduced (relative to legacy UEs), a single receive radio frequency(RF) chain may be used, peak rate may be reduced (e.g., a maximum of1000 bits for a transport block size), transmit power may be reduced,Rank 1 transmission may be used, and half duplex operation may beperformed.

In some cases, if half-duplex operation is performed, MTC UEs may have arelaxed switching time to transition from transmitting to receiving (orreceiving to transmitting). For example, the switching time may berelaxed from 20 μs is for regular UEs to 1 ms for MTC UEs. Release 12MTC UEs may still monitor downlink (DL) control channels in the same wayas regular UEs, for example, monitoring for wideband control channels inthe first few symbols (e.g., PDCCH) as well as narrowband controlchannels occupying a relatively narrowband, but spanning a length of asubframe (e.g., enhanced PDCCH or ePDCCH).

Certain standards (e.g., LTE Release 13) may introduce support forvarious additional MTC enhancements, referred to herein as enhanced MTC(or eMTC). For example, eMTC may provide MTC UEs with coverageenhancements up to 15 dB.

As illustrated in the subframe structure 500 of FIG. 5, eMTC UEs cansupport narrowband operation while operating in a wider system bandwidth(e.g., 1.4/3/5/10/15/20 MHz). In the example illustrated in FIG. 5, aconventional legacy control region 510 may span system bandwidth of afirst few symbols, while a narrowband region 530 of the system bandwidth(spanning a narrow portion of a data region 520) may be reserved for anMTC physical downlink control channel (referred to herein as an M-PDCCH)and for an MTC physical downlink shared channel (referred to herein asan M-PDSCH). In some cases, an MTC UE monitoring the narrowband regionmay operate at 1.4 MHz or 6 resource blocks (RBs).

However, as noted above, eMTC UEs may be able to operate in a cell witha bandwidth larger than 6 RBs. Within this larger bandwidth, each eMTCUE may still operate (e.g., monitor/receive/transmit) while abiding by a6-physical resource block (PRB) constraint. In some cases, differenteMTC UEs may be served by different narrowband regions (e.g., with eachspanning 6-PRB blocks). As the system bandwidth may span from 1.4 to 20MHz, or from 6 to 100 RBs, multiple narrowband regions may exist withinthe larger bandwidth. An eMTC UE may also switch or hop between multiplenarrowband regions in order to reduce interference.

EXAMPLE NARROWBAND INTERNET-OF-THINGS (NB-IOT)

The Internet-of-Things (IoT) may refer to a network of physical objects,devices, or “things”. IoT devices may be embedded with, for example,electronics, software, or sensors and may have network connectivity,which enable these devices to collect and exchange data. IoT devices maybe sensed and controlled remotely across existing networkinfrastructure, creating opportunities for more direct integrationbetween the physical world and computer-based systems and resulting inimproved efficiency, accuracy, and economic benefit. Systems thatinclude IoT devices augmented with sensors and actuators may be referredto cyber-physical systems. Cyber-physical systems may includetechnologies such as smart grids, smart homes, intelligenttransportation, and/or smart cities. Each “thing” (e.g., IoT device) maybe uniquely identifiable through its embedded computing system may beable to interoperate within existing infrastructure, such as Internetinfrastructure.

Narrowband IoT (NB-IoT) may refer to a narrowband radio technologyspecially designed for the IoT. NB-IoT may focus on indoor coverage, lowcost, long battery life, and large number of devices. To reduce thecomplexity of UEs, NB-IoT may allow for narrowband deployments utilizingone physical resource block (PRB) (e.g., 180 kHz+20 kHz guard band).NB-IoT deployments may utilize higher layer components of certainsystems (e.g., LTE) and hardware to allow for reduced fragmentation andcross compatibility with, for example, NB-LTE and/or enhanced/evolvedmachine type communications (eMTC).

FIG. 6 illustrates an example deployment 600 of NB-IoT, according tocertain aspects of the present disclosure. Three NB-IoT deploymentconfigurations include in-band, guard-band, and standalone. For thein-band deployment configuration, NB-IoT may coexist with a legacysystem (e.g., GSM, WCDMA, and/or LTE system(s)) deployed in the samefrequency band. For example, the wideband LTE channel may be deployed invarious bandwidths between 1.4 MHz to 20 MHz. As shown in FIG. 6, adedicated resource block (RB) 602 within that bandwidth may be availablefor use by NB-IoT and/or the RBs 1204 may be dynamically allocated forNB-IoT. As shown in FIG. 6, in an in-band deployment, one RB, or 200kHz, of a wideband channel (e.g., LTE) may be used for NB-IoT.

Certain systems (e.g., LTE) may include unused portions of the radiospectrum between carriers to guard against interference between adjacentcarriers. In some deployments, NB-IoT may be deployed in a guard band606 of the wideband channel.

In other deployments, NB-IoT may be deployed standalone (not shown). Ina standalone deployment, one 200 MHz carrier may be utilized to carryNB-IoT traffic and GSM spectrum may be reused.

Deployments of NB-IoT may include synchronization signals such as PSSfor frequency and timing synchronization and SSS to convey systeminformation. For NB-IoT operations, PSS/SSS timing boundaries may beextended as compared to the existing PSS/SSS frame boundaries in legacysystems (e.g., LTE), for example, from 10 ms to 40 ms. Based on thetiming boundary, a UE is able to receive a PBCH transmission, which maybe transmitted in subframe 0 of a radio frame.

EXAMPLE NR/5G RAN ARCHITECTURE

New radio (NR) may refer to radios configured to operate according to anew air interface (e.g., other than Orthogonal Frequency DivisionalMultiple Access (OFDMA)-based air interfaces) or fixed transport layer(e.g., other than Internet Protocol (IP)). NR may utilize OFDM with a CPon the uplink and downlink and include support for half-duplex operationusing TDD. NR may include Enhanced Mobile Broadband (eMBB) servicetargeting wide bandwidth (e.g. 80 MHz beyond), millimeter wave (mmW)targeting high carrier frequency (e.g. 27 GHz or beyond), massive MTC(mMTC) targeting non-backward compatible MTC techniques, and/or missioncritical targeting ultra reliable low latency communications (URLLC)service.

A single component carrier bandwidth of 100 MHZ may be supported. NRresource blocks may span 12 sub-carriers with a sub-carrier bandwidth of75 kHz over a 0.1 ms duration. Each radio frame may have a length intime of 10 milliseconds (ms) and may consist of 2 half frames, each halfframe consisting of 5 subframes. Consequently, each subframe may have alength of 1 ms. Each subframe may indicate a link direction (i.e., DL orUL) for data transmission and the link direction for each subframe maybe dynamically switched. Each subframe may include DL/UL data as well asDL/UL control data. UL and DL subframes for NR may be as described inmore detail below with respect to FIGS. 9 and 10.

Beamforming may be supported and beam direction may be dynamicallyconfigured. MIMO transmissions with precoding may also be supported.MIMO configurations in the DL may support up to 8 transmit antennas withmulti-layer DL transmissions up to 8 streams and up to 2 streams per UE.Multi-layer transmissions with up to 2 streams per UE may be supported.Aggregation of multiple cells may be supported with up to 8 servingcells. Alternatively, NR may support a different air interface, otherthan an OFDM-based interface. NR networks may include entities suchcentral units or distributed units

The RAN may include a central unit (CU) and distributed units (DUs). ANR BS (e.g., gNB, 5G Node B, Node B, transmission reception point (TRP),access point (AP)) may correspond to one or multiple BSs. NR cells canbe configured as access cells (ACells) or data only cells (DCells). Forexample, the RAN (e.g., a central unit or distributed unit) canconfigure the cells. DCells may be cells used for carrier aggregation ordual connectivity, but not used for initial access, cellselection/reselection, or handover. In some cases DCells may nottransmit synchronization signals—in some case cases DCells may transmitSS. NR BSs may transmit downlink signals to UEs indicating the celltype. Based on the cell type indication, the UE may communicate with theNR BS. For example, the UE may determine NR BSs to consider for cellselection, access, handover, and/or measurement based on the indicatedcell type.

FIG. 7 illustrates an example logical architecture of a distributed RAN700, according to aspects of the present disclosure. A 5G access node706 may include an access node controller (ANC) 702. The ANC may be acentral unit (CU) of the distributed RAN 700. The backhaul interface tothe next generation core network (NG-CN) 704 may terminate at the ANC.The backhaul interface to neighboring next generation access nodes(NG-ANs) may terminate at the ANC. The ANC may include one or more TRPs708 (which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs,or some other term). As described above, a TRP may be usedinterchangeably with “cell.”

The TRPs 708 may be a distributed unit (DU). The TRPs may be connectedto one ANC (ANC 702) or more than one ANC (not illustrated). Forexample, for RAN sharing, radio as a service (RaaS), and servicespecific AND deployments, the TRP may be connected to more than one ANC.A TRP may include one or more antenna ports. The TRPs may be configuredto individually (e.g., dynamic selection) or jointly (e.g., jointtransmission) serve traffic to a UE.

The local architecture 700 may be used to illustrate fronthauldefinition. The architecture may be defined that support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE.According to aspects, the next generation AN (NG-AN) 710 may supportdual connectivity with NR. The NG-AN may share a common fronthaul forLTE and NR.

The architecture may enable cooperation between and among TRPs 708. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 702. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture 700. The PDCP, RLC, MAC protocolmay be adaptably placed at the ANC or TRP.

According to certain aspects, a BS may include a central unit (CU)(e.g., ANC 702) and/or one or more distributed units (e.g., one or moreTRPs 708).

FIG. 8 illustrates an example physical architecture of a distributed RAN800, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 802 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 804 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C-RUmay have distributed deployment. The C-RU may be closer to the networkedge.

A distributed unit (DU) 706 may host one or more TRPs. The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 9 is a diagram 900 showing an example of a DL-centric subframe. Asubframe may comprise a number of slots, for example, one or more DLslots and/or UL slots. A DL-centric subframe may comprise more DL slotsthan UL slots. The DL-centric subframe, as shown in FIG. 9, may includea control portion 902. The control portion 902 may exist in the initialor beginning portion of the DL-centric subframe. The control portion 902may include various scheduling information and/or control informationcorresponding to various portions of the DL-centric subframe. In someconfigurations, the control portion 902 may be a physical DL controlchannel (PDCCH), as indicated in FIG. 9. The DL-centric subframe mayalso include a DL data portion 904. The DL data portion 904 maysometimes be referred to as the payload of the DL-centric subframe. TheDL data portion 904 may include the communication resources utilized tocommunicate DL data from the scheduling entity (e.g., UE or BS) to thesubordinate entity (e.g., UE). In some configurations, the DL dataportion 904 may be a physical DL shared channel (PDSCH).

The DL-centric subframe may also include a common UL portion 906. Thecommon UL portion 906 may sometimes be referred to as an UL burst, acommon UL burst, and/or various other suitable terms. The common ULportion 906 may include feedback information corresponding to variousother portions of the DL-centric subframe. For example, the common ULportion 906 may include feedback information corresponding to thecontrol portion 902. Non-limiting examples of feedback information mayinclude an ACK signal, a NACK signal, a HARQ indicator, and/or variousother suitable types of information. The common UL portion 906 mayinclude additional or alternative information, such as informationpertaining to random access channel (RACH) procedures, schedulingrequests (SRs), and various other suitable types of information. Asillustrated in FIG. 9, the end of the DL data portion 904 may beseparated in time from the beginning of the common UL portion 906. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric subframe and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 10 is a diagram 1000 showing an example of an UL-centricsubframe._As noted above, a subframe may comprise a number of slotsincluding one or more DL slots and/or UL slots. A UL-centric subframemay comprise more UL slots than DL slots. The UL-centric subframe, asshown in FIG. 10, may include a control portion 1002. The controlportion 1002 may exist in the initial or beginning portion of theUL-centric subframe. The control portion 1002 in FIG. 10 may be similarto the control portion 1002 described above with reference to FIG. 9.The UL-centric subframe may also include an UL data portion 1004. The ULdata portion 1004 may sometimes be referred to as the payload of theUL-centric subframe. The UL portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., UE) to the scheduling entity (e.g., UE or BS). In someconfigurations, the control portion 1002 may be a physical uplinkcontrol channel (PUCCH). In some configurations, the data portion may bea physical uplink shared channel (PUSCH).

As illustrated in FIG. 10, the end of the control portion 1002 may beseparated in time from the beginning of the UL data portion 1004. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe may alsoinclude a common UL portion 1006. The common UL portion 1006 in FIG. 10may be similar to the common UL portion 1006 described above withreference to FIG. 10. The common UL portion 1006 may additional oralternative include information pertaining to channel quality indicator(CQI), sounding reference signals (SRSs), and various other suitabletypes of information. One of ordinary skill in the art will understandthat the foregoing is merely one example of an UL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an access node (AN), or adistributed unit (DU), or portions thereof Each receiving network accessdevice may be configured to receive and measure pilot signalstransmitted on the common set of resources, and also receive and measurepilot signals transmitted on dedicated sets of resources allocated tothe UEs for which the network access device is a member of a monitoringset of network access devices for the UE. One or more of the receivingnetwork access devices, or a central unit (CU) to which receivingnetwork access device(s) transmit the measurements of the pilot signals,may use the measurements to identify serving cells for the UEs, or toinitiate a change of serving cell for one or more of the UEs.

EXAMPLE NEIGHBOR CELL MEASUREMENT AND RESELECTION FOR NARROWBANDOPERATION

Aspects of the present disclosure provide techniques that may beutilized by a UE for performing neighbor cell measurement andreselection in narrowband deployment scenarios, such as NB-IoTdeployment scenarios.

To ensure reliable performance, UEs operating in a current serving cellare typically configured to perform reselection to a strong neighborcell. To perform reselection, a UE is typically expected to perform aneighbor cell search on the same E-UTRA Absolute Radio Frequency ChannelNumber (EARFCN) as the serving cell in order to find suitableintra-frequency neighbor cells or to retune to another EARFCN to findinter-frequency neighbor cells.

Upon finding strong neighbor cells on the EARFCN, a UE may perform anarrowband reference signal receive power (NRSRP) measurement on theneighbor cells. The UE may also make decisions based on a comparison ofthe neighbor cell NRSRP to the serving cell NRSRP. For example, if theneighbor cell NRSP exceeds the serving cell NRSP by a threshold amount:

neighbor_NRSRP−serving_NRSRP>threshold,

the UE may reselect to the neighbor cell. Reselecting to the neighborcell may involve a narrowband PBCH (NPBCH) decode followed by decodingof SIBs and then camping on the (target) neighbor cell.

Challenges are presented when performing neighbor cell measurement andreselection, however, when a UE does not have knowledge of transmissiondeployment parameters of the neighbor cells.

In some cases, in an NB-IoT deployment configuration, NB-IoT eNBs may beconfigured to operate with either one Tx antenna or two Tx antenna thatare used for transmit diversity (TxD). It may be expected thatstandalone deployments may only support one Tx antenna. This may bebecause GSM cells may be reused/reframed for NB-IoT deployment. On theother hand, in-band and guard band cells may most likely support two Txantennas, because many LTE cells use at least two Tx antennas.

Different deployment modes may also use different frequency resources,with raster offsets from reference frequencies. In some cases, forin-band deployment modes, NB-IoT cells may only be present on certainpredefined LTE PRBs (PRBs within LTE system bandwidth) which have araster offset of either 0 KHz, +/−2.5 KHz or +/−7.5 KHz. Guard banddeployment modes may use raster offsets that are the same or similar tothose in an in-band case. Standalone deployment mode cells, on the otherhand, may be deployed on a 100 KHz raster. In some cases, a UE mayacquire both a deployment mode and a TxD mode of the cell from the MIBafter an NPBCH decode.

To prevent UEs from occupying DL resources for too long with longrepetitions in the extreme coverage mode, DL subframes may be marked asvalid or invalid for NB-PDCCH and NB-PDSCH (except SIBs) transmission asfollows. Narrowband reference signals (NRS) may not be present insubframes considered invalid subframes. NB-IoT DL (valid/invalid)subframe configuration is typically set by an optional bit-map(downlinkBitmapNB) for the anchor PRB and another bit-map(downlinkBitmapNB-additional) for the non-anchor PRB, carried byNB-SIB1. The bitmaps vary depending on deployment mode. For example, forin-band deployment, a 10-bit bit-mask for 10 ms or 40-bit bit-mask for40 ms (aligned to SFN mod 4) may be used. For guard-band and stand-alonemodes, a 10-bit bit-mask for 10 ms may be used.

In some cases, this may mean NRS availability (via the DL valid/invalidbit-mask) for a cell may not be known until after decoding SIB1. Lack ofknowledge of the transmission deployment parameters present challengeswhen performing neighbor cell measurement and reselection. In somecases, when certain cell reselection criteria (“S criteria”) to performneighbor cell search and measurement are met (e.g., Srxlev<Sintrasearchor Srxlev<Snonintrasearch), the UE is unaware of the neighbor celldeployment configuration.

In some cases, the UE may not know the TxD mode of neighbor cell, soNRSRP measurement may be inaccurate (e.g., positively or negativelybiased) due to incorrect TxD mode assumption. Further, the UE may notknow the valid subframe configuration of the neighbor cell and, thus,NRSRP measurement can be challenging and inaccuracy may be high (e.g.,especially if the UE is in enhanced coverage of the neighbor cell).Inaccuracy in measurement, regardless of the reason, may result inincorrect reselection decision (i.e. not reselecting to a stronger cell)or potentially reselecting to a weaker cell because the neighbor cellmeasurement may be biased.

In addition, the UE may also not know the raster offset of the neighborcell (e.g., with respect to the 100 KHz raster), so cellsearch/measurement may fail if the UE only searches on the 100 KHzraster points. Due to the high number of possible raster offsetpossibilities, cell search time/complexity increases if raster offset(or other information about a raster) has to be inferred by UE.

FIG. 11 illustrates example operations 1100 that may be performed, forexample, by a UE as part of a neighbor cell measurement and reselectionprocedure.

The UE operations 1100 begin, at 1102, by determining, whilecommunicating in a serving cell, information regarding one or moretransmission deployment mode parameters of at least one neighbor cell.At 1104, the UE performs a neighbor cell search with measurement ofnarrowband reference signals (NRS) based on the one or more transmissiondeployment mode parameters.

The UE may determine the transmission deployment mode parameters invarious ways, depending on a particular implementation. In some cases, anetwork may signal neighbor cell transmission deployment modeparameters, such as TxD mode, raster offset, and DL valid bit mask.These parameters may be signaled in broadcast messages, such as SIB3,SIB4, or SIB5 of the serving cell. Such signaling may be implemented viaa standard specification change. One advantage to this approach may bethat a UE's neighbor NRSRP measurement accuracy may be more accurate ifTxD mode is known. In some cases, the UE can correctly measure on thesub frames carrying NRS and can also account for the possibility ofneighbor NRSRP measurement inaccuracy when triggering reselection if DLvalid bit mask is known. Further, the UE's neighbor cell searchtime/complexity can be reduced significantly if raster offset is known.

In some cases, the UE can infer the neighbor cell transmissiondeployment parameters (or account for lack of knowledge of theseparameters) during neighbor cell search and measurements. For example,the UE may include one or more operations for inferring informationabout a raster offset. In some cases, the UE may include evaluating aplurality of different hypotheses for different frequency errors to findframe and symbol timing. The UE may also include using one of theplurality of different hypotheses, selected based on the evaluation, todetect narrowband primary synchronization signals (NPSS) and narrowbandsecondary synchronization signals

Regarding TxD mode inference, NRSRP estimation may be performed on a perTx antenna basis by coherently averaging available NRS tones across 40ms and then non-coherently averaging the results across multipleconsecutive 40 ms durations making up the measurement period. If thecell has one Tx antennas, the NRSRP estimate of that Tx antenna may bereported after subtracting RF offset. If the cell has two Tx antennas,the sum of NRSRP estimates per Tx antenna may be reported aftersubtracting RF offset.

If the TxD mode is known (e.g., after MIB decode on a cell), NRSRPestimation can be done appropriately based on one Tx or two Tx antennasper the cell's TxD mode.

If the TxD mode is unknown (e.g., before MIB decode), the UE mayevaluate multiple hypotheses regarding the number of Tx antennas. Forexample, in some cases, a UE may infer a number of transmit antennasused by the neighbor cell by evaluating different hypothesescorresponding to different numbers of transmit antennas, and may selectone of the different hypotheses with a higher NRS receive power (NRSRP)than another. In some cases, the UE can perform a hypothesis testing ofboth cases (e.g., assume one Tx antenna and two Tx antenna scenarios)and pick the max of the two. In this manner, the NRSRP estimate and TxDmode of the cell can be inferred even before MIB decode.

In some cases, the UE may take action for neighbor measurement and cellreselection when a DL valid bit map is unknown. In some cases, the UEmay perform NRSRP measurement while assuming the worst case availabilitypattern of NRS with a minimum amount of subframes with NRS availability(e.g., SF#0 and SF#4 of every frame and SF#9 of every other frame). Thismay imply, in enhanced coverage (CINR<-6 dB), that measurementinaccuracy can be very high due to low NRS density. In some cases, whenthe serving cell and neighbor cell are both in enhanced coverage(CINR<-6 dB), this may lead to high measurement inaccuracy (e.g., highbias in NRSRP measurement) that can lead to small separation in measuredNRSRP per cell, even though the actual CINR difference is large.

In some cases, a UE (physical layer ML1) may be scheduled for multipleback to back measurements on a cell and/or maintain a list/history, forexample, of last measurements (e.g., measured within the last 2 sec) oneach cell. In some cases, the list may be sorted (by ML1) by NRSRP percell. When comparing NRSRP of serving and target cell, the UE (ML1) maypick the median of the sorted list of each cell and compare thedifference of the medians against a pre-defined threshold.

When the DL valid bit map is unknown, a UE may evaluate multiplehypotheses to perform neighbor cell measurement and reselection. Forexample, NRSRP measurement may be performed with all possible DL validbit mask hypotheses and the one with the maximum NRSRP estimate can beused to determine the DL valid bit mask configured on neighbor cell andthe associated NRSRP can be used for reselection triggering. Oneadvantage to this approach may be that subsequent NPBCH decoding on atarget cell can be run with the resulting hypothesis of DL valid maskand thus save some current consumption

Regarding neighbor cell raster offset, as noted above, in some cases theserving cell may signal the neighbor cell's raster offset in SIBs toreduce cell search time/complexity.

If such signaling is not available, the UE may perform an initialacquisition (on the EARFCN) just to determine the total frequencyoffset. The UE may then apply the total frequency offset at the rotator.In some cases, the UE applies the total frequency offset beforecontinuing to refine the frame and symbol timing, residual frequencyerror, and finding the physical cell Identifier (PCID). Under certainconditions, running initial acquisition may take a long time and, thus,may adversely impact power consumption. As an example, around 500 ms@CINR=−12.6 dB there may be an adverse impact on power consumption.

As an alternative, a UE may evaluate a limited number of hypotheses. Forexample, the UE may maintain five different frequency error hypotheses(e.g., 0 KHz, +/−2.5KHz, +/−7.5KHz) and, for each frequency hypotheses,the UE can start with cross correlation based narrowband PSS (NPSS)detection followed by narrowband SSS (NSSS) detection to find the frameand symbol timing, residual frequency error, and find the PCID. Whileinitial acquisition time may be saved with this approach, evaluatingfive hypotheses in parallel (with higher searcher processing horsepower)or running them serially (with increased search time) may also adverselyimpact current consumption.

Techniques presented herein may be used by a UE to help perform neighborcell measurement and reselection, even when neighbor cell transmissiondeployment mode parameters are not known.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase, for example, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, forexample the phrase “X employs A or B” is satisfied by any of thefollowing instances: X employs A; X employs B; or X employs both A andB. As used herein, reference to an element in the singular is notintended to mean “one and only one” unless specifically so stated, butrather “one or more.” For example, the articles “a” and “an” as used inthis application and the appended claims should generally be construedto mean “one or more” unless specified otherwise or clear from thecontext to be directed to a singular form. Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as wellas any combination with multiples of the same element (e.g., a-a, a-a-a,a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or anyother ordering of a, b, and c). As used herein, including in the claims,the term “and/or,” when used in a list of two or more items, means thatany one of the listed items can be employed by itself, or anycombination of two or more of the listed items can be employed. Forexample, if a composition is described as containing components A, B,and/or C, the composition can contain A alone; B alone; C alone; A and Bin combination; A and C in combination; B and C in combination; or A, B,and C in combination.

As used herein, the term “identifying” encompasses a wide variety ofactions. For example, “identifying” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “identifying” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“identifying” may include resolving, selecting, choosing, establishingand the like.

In some cases, rather than actually communicating a frame, a device mayhave an interface to communicate a frame for transmission or reception.For example, a processor may output a frame, via a bus interface, to anRF front end for transmission. Similarly, rather than actually receivinga frame, a device may have an interface to obtain a frame received fromanother device. For example, a processor may obtain (or receive) aframe, via a bus interface, from an RF front end for transmission.

The methods described herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Softwareshall be construed broadly to mean instructions, instruction sets, code,code segments, program code, programs, subprograms, software modules,applications, software applications, software packages, firmware,routines, subroutines, objects, executables, threads of execution,procedures, functions, etc., whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Generally, where there are operations illustrated in Figures, thoseoperations may be performed by any suitable corresponding counterpartmeans-plus-function components. For example, operations 1100 (1102,1104) illustrated in FIG. 11 correspond to means 1100A (1102A, 1104A)illustrated in FIG. 11A.

For example, means for determining, means for performing, means forinferring, means for applying, means for transmitting, means forreceiving, means for sending, means for applying, means for selecting,means for using, means for evaluating, and/or means for measuring mayinclude one or more processors or other elements, such as the transmitprocessor 264, the controller/processor 280, the receive processor 258,and/or antenna(s) 252 of the user equipment 120 illustrated in FIG. 2,and/or the transmit processor 220, the controller/processor 240, and/orantenna(s) 234 of the base station 110 illustrated in FIG. 2.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or combinations thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, software, or combinations thereof. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination thereof. A softwaremodule may reside in RAM memory, flash memory, ROM memory, EPROM memory,EEPROM memory, phase change memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, or combinations thereof. Ifimplemented in software, the functions may be stored on or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD/DVD or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the subject matter of thedisclosure. Various modifications to the disclosure will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other variations without departing from thespirit or scope of the disclosure. Thus, the disclosure is not intendedto be limited to the examples and designs described herein but is to beaccorded the widest scope consistent with the principles and novelfeatures described herein.

What is claimed is:
 1. A method for wireless communications by a userequipment (UE), comprising: determining, while communicating in aserving cell, information regarding one or more transmission deploymentmode parameters of at least one neighbor cell; and performing a neighborcell search with measurement of narrowband reference signals (NRS) basedon the one or more transmission deployment mode parameters.
 2. Themethod of claim 1, wherein the one or more transmission deployment modeparameters comprise at least one of: a number of transmit antennas usedby the neighbor cell, a raster offset of physical resource blocks(PRBs), or information regarding availability of NRS in subframes. 3.The method of claim 1, wherein the determination is based on broadcastsignaling of the one or more transmission deployment mode parameters inthe serving cell.
 4. The method of claim 1, wherein the determiningcomprises: inferring a number of transmit antennas used by the at leastone neighbor cell by evaluating different hypotheses corresponding todifferent numbers of transmit antennas; and selecting one of thedifferent hypotheses with a higher NRS receive power (NRSRP) thananother.
 5. The method of claim 1, wherein: the determining comprisesdetermining information regarding availability of NRS in subframes forthe at least one neighbor cell is unknown; and the performing theneighbor cell search with measurement comprises assuming a worst casepattern of subframes with a minimum amount of subframes with NRSavailability.
 6. The method of claim 1, wherein: the determiningcomprises inferring information regarding availability of NRS insubframes for the at least one neighbor cell by evaluating differenthypotheses regarding different subframe bitmaps and selecting one of thedifferent hypotheses with a higher NRS receive power (NRSRP) thananother.
 7. The method of claim 6, further comprising using the NRSRP ofthe selected hypothesis for reselection triggering.
 8. The method ofclaim 6, further comprising using the selected hypothesis for decoding anarrowband physical broadcast channel (NPBCH) in the at least oneneighbor cell.
 9. The method of claim 1, wherein the determiningcomprises inferring information about a raster offset by: performing aninitial acquisition in the at last one neighbor cell to determine atotal frequency offset; and applying the total frequency offset beforerefining frame and symbol timing, residual frequency error, anddetermining a physical cell ID (PCID) of the at least one neighbor cell.10. The method of claim 1, wherein the determining comprises inferringinformation about a raster offset by: evaluating a plurality ofdifferent hypotheses for different frequency errors to find frame andsymbol timing; and using one of the plurality of different hypotheses,selected based on the evaluation, to detect narrowband primarysynchronization signals (NPSS) and narrowband secondary synchronizationsignals.
 11. An apparatus for wireless communications by a userequipment (UE), comprising: means for determining, while communicatingin a serving cell, information regarding one or more transmissiondeployment mode parameters of at least one neighbor cell; and means forperforming a neighbor cell search with measurement of narrowbandreference signals (NRS) based on the one or more transmission deploymentmode parameters.
 12. The apparatus of claim 11, wherein the one or moretransmission deployment mode parameters comprise at least one of: anumber of transmit antennas used by the neighbor cell, a raster offsetof physical resource blocks (PRBs), or information regardingavailability of NRS in subframes.
 13. The apparatus of claim 11, whereinthe determination is based on broadcast signaling of the one or moretransmission deployment mode parameters in the serving cell.
 14. Theapparatus of claim 11, wherein the means for determining comprises:means for inferring a number of transmit antennas used by the at leastone neighbor cell by evaluating different hypotheses corresponding todifferent numbers of transmit antennas; and means for selecting one ofthe different hypotheses with a higher NRS receive power (NRSRP) thananother.
 15. The apparatus of claim 11, wherein: the means fordetermining comprises means for determining information regardingavailability of NRS in subframes for the at least one neighbor cell isunknown; and the means for performing the neighbor cell search withmeasurement comprises means for assuming a worst case pattern ofsubframes with a minimum amount of subframes with NRS availability. 16.The apparatus of claim 11, wherein: the means for determining comprisesmeans for inferring information regarding availability of NRS insubframes for the at least one neighbor cell by evaluating differenthypotheses regarding different subframe bitmaps and selecting one of thedifferent hypotheses with a higher NRS receive power (NRSRP) thananother.
 17. The apparatus of claim 16, further comprising means forusing the NRSRP of the selected hypothesis for reselection triggering.18. The apparatus of claim 16, further comprising means for using theselected hypothesis for decoding a narrowband physical broadcast channel(NPBCH) in the at least one neighbor cell.
 19. The apparatus of claim11, wherein the means for determining comprises means for inferringinformation about a raster offset that includes: means for performing aninitial acquisition in the at last one neighbor cell to determine atotal frequency offset; and means for applying the total frequencyoffset before refining frame and symbol timing, residual frequencyerror, and means for determining a physical cell ID (PCID) of the atleast one neighbor cell.
 20. The apparatus of claim 11, wherein themeans for determining comprises means for inferring information about araster offset that includes: means for evaluating a plurality ofdifferent hypotheses for different frequency errors to find frame andsymbol timing; and means for using one of the plurality of differenthypotheses, selected based on the evaluation, to detect narrowbandprimary synchronization signals (NPSS) and narrowband secondarysynchronization signals.
 21. An apparatus for wireless communication bya user equipment (UE), comprising: at least one processor configured to:determine, while communicating in a serving cell, information regardingone or more transmission deployment mode parameters of at least oneneighbor cell; and perform a neighbor cell search with measurement ofnarrowband reference signals (NRS) based on the one or more transmissiondeployment mode parameters; and a memory coupled to the at least oneprocessor.
 22. A non-transitory computer readable medium for wirelesscommunication by a user equipment (UE) having instructions storedthereon for: determining, while communicating in a serving cell,information regarding one or more transmission deployment modeparameters of at least one neighbor cell; and performing a neighbor cellsearch with measurement of narrowband reference signals (NRS) based onthe one or more transmission deployment mode parameters.